This invention relates to imaging of materials, and more particularly, relates to imaging materials to determine selected petrophysical properties.
Welge and conventional centrifuge methods for measuring relative permeability of a porous material, as well as the centrifuge method for measuring capillary pressure, all use effluent data to calculate saturations at either the inflow or outflow ends of the sample of material, usually an earthen core sample. On the other hand, the steady-state method for measuring relative permeabilities, as well as the capillary diaphragm and mercury injection methods for measuring capillary pressures, assume uniform saturations in a sample.
In general, the previous prior art methods for measuring relative permeability assume capillary pressure effects are negligible. And, conversely, the prior art capillary pressure methods assume relative permeability effects are negligible. These assumptions, however, are not always satisfied. Such methods, which depend on effluent data are, therefore, incorrect to the extent that the model for reconstructing saturation profiles is influenced by the effect assumed negligible. for example, a problem with the Welge method is that it ignores any capillary end effect. Further, the methods which rely on uniform saturation are incorrect to the extent that the neglected effect prevents obtaining uniform saturations. For example, the low relative permeability of the displaced phase in the capillary diaphragm method can result in inordinately long times to reach uniform saturations.
These and other limitations and disadvantages of prior art are overcome by the present invention and improved methods and apparatus are provided for measuring selected petrophysical properties, such as capillary pressure and/or relative permeability, of a material or fluids therein.